diff --git a/lib/Db/CredentialMapper.php b/lib/Db/CredentialMapper.php
index 49697780..060940a0 100644
--- a/lib/Db/CredentialMapper.php
+++ b/lib/Db/CredentialMapper.php
@@ -32,12 +32,21 @@ class CredentialMapper extends Mapper {
 		return $this->findEntities($sql, [$user_id, $vault_id]);
 	}
 
+	/**
+	 * @param $vault_id
+	 * @param $user_id
+	 * @return Credential[]
+	 */
 	public function getRandomCredentialByVaultId($vault_id, $user_id) {
 		$sql = 'SELECT * FROM `*PREFIX*passman_credentials` ' .
 			'WHERE `user_id` = ? and vault_id = ? AND shared_key is NULL ORDER BY RAND() LIMIT 1';
 		return $this->findEntities($sql, [$user_id, $vault_id]);
 	}
 
+	/**
+	 * @param $timestamp
+	 * @return Credential[]
+	 */
 	public function getExpiredCredentials($timestamp){
 		$sql = 'SELECT * FROM `*PREFIX*passman_credentials` ' .
 			'WHERE `expire_time` > 0 AND `expire_time` < ?';
diff --git a/tests/db/DatabaseHelperTest.php b/tests/db/DatabaseHelperTest.php
index 6181f193..edc50673 100644
--- a/tests/db/DatabaseHelperTest.php
+++ b/tests/db/DatabaseHelperTest.php
@@ -81,7 +81,14 @@ abstract class DatabaseHelperTest extends PHPUnit_Extensions_Database_TestCase {
 			$qb->insert($table_no_prefix);
 
 			foreach ($row as $key => $value){
-				$qb->setValue($key, is_numeric($value) ? $value : ("'{$value}'"));
+				if (is_null($value)) {
+					$value = 'NULL';
+				}
+				else if (!is_numeric($value)) {
+					$value = "'{$value}'";
+				}
+
+				$qb->setValue($key,  $value);
 			}
 
 			$qb->execute();
@@ -114,7 +121,7 @@ abstract class DatabaseHelperTest extends PHPUnit_Extensions_Database_TestCase {
 		$result = [];
 		for ($i = 0; $i < $rows; $i++) {
 			$row = $table->getRow($i);
-			if ($row[$field_name] === $value_match){
+			if ($row[$field_name] == $value_match){
 				$result[] = $row;
 			}
 		}
@@ -132,7 +139,7 @@ abstract class DatabaseHelperTest extends PHPUnit_Extensions_Database_TestCase {
 		$ret = [];
 
 		foreach ($dataset as $value){
-			if ($value[$field_name] === $value_match){
+			if ($value[$field_name] == $value_match){
 				$ret[] = $value;
 			}
 		}
diff --git a/tests/db/dumps/oc_passman_credentials.xml b/tests/db/dumps/oc_passman_credentials.xml
index fd0d05cd..d2278ef8 100644
--- a/tests/db/dumps/oc_passman_credentials.xml
+++ b/tests/db/dumps/oc_passman_credentials.xml
@@ -90,7 +90,7 @@
 		<field name="url">eyJpdiI6Ikg2UC96K1dmdGRZN0VhYU1XV1ZsQlEiLCJ2IjoxLCJpdGVyIjoxMDAwLCJrcyI6MjU2LCJ0cyI6NjQsIm1vZGUiOiJjY20iLCJhZGF0YSI6IiIsImNpcGhlciI6ImFlcyIsInNhbHQiOiJEN1Y1Z0VYbWt6NCIsImN0IjoibFhvV25sVTluZStDQklkNCJ9</field>
 		<field name="favicon" xsi:nil="true" />
 		<field name="renew_interval" xsi:nil="true" />
-		<field name="expire_time">0</field>
+		<field name="expire_time">150</field>
 		<field name="delete_time">0</field>
 		<field name="files">eyJpdiI6Ijh4UTJ4ZlF5YXlJN25CYXAvUGtMWGciLCJ2IjoxLCJpdGVyIjoxMDAwLCJrcyI6MjU2LCJ0cyI6NjQsIm1vZGUiOiJjY20iLCJhZGF0YSI6IiIsImNpcGhlciI6ImFlcyIsInNhbHQiOiJEN1Y1Z0VYbWt6NCIsImN0IjoiQU9oUDBiamE0ZmxGL1EifQ==</field>
 		<field name="custom_fields">eyJpdiI6Ik1QM1RPZXl1dWNzZEtiVS9ucm0vaEEiLCJ2IjoxLCJpdGVyIjoxMDAwLCJrcyI6MjU2LCJ0cyI6NjQsIm1vZGUiOiJjY20iLCJhZGF0YSI6IiIsImNpcGhlciI6ImFlcyIsInNhbHQiOiJEN1Y1Z0VYbWt6NCIsImN0IjoiSlBlMExLMWIvdTdMTkEifQ==</field>
diff --git a/tests/unit/lib/Db/CredentialMapperTest.php b/tests/unit/lib/Db/CredentialMapperTest.php
new file mode 100644
index 00000000..e9f95634
--- /dev/null
+++ b/tests/unit/lib/Db/CredentialMapperTest.php
@@ -0,0 +1,125 @@
+<?php
+
+/**
+ *
+ * Date: 15/10/16
+ * Time: 20:06
+ *
+ * @copyright Copyright (c) 2016, Marcos Zuriaga Miguel (wolfi@wolfi.es)
+ * @license AGPLv3
+ */
+use \OCA\Passman\Db\CredentialMapper;
+use \OCA\Passman\Db\Credential;
+use \OCA\Passman\Utility\Utils;
+
+/**
+ * @coversDefaultClass \OCA\Passman\Db\CredentialMapper
+ */
+class CredentialMapperTest extends DatabaseHelperTest {
+	CONST TABLES = [
+		'oc_passman_credentials'
+	];
+
+	/**
+	 * @var CredentialMapper
+	 */
+	protected $mapper;
+
+	/**
+	 * @var PHPUnit_Extensions_Database_DataSet_ITable
+	 */
+	protected $dataset;
+
+	/**
+	 * @after
+	 */
+	public function setUp() {
+		parent::setUp();
+		$this->mapper = new CredentialMapper($this->db, new Utils());
+		$this->dataset = $this->getTableDataset(self::TABLES[0]);
+	}
+
+	/**
+	 * This function should return the table name, for example
+	 * for a test running on oc_passman_vaults it shall return ["oc_passman_vaults"]
+	 *
+	 * @internal
+	 * @return string[]
+	 */
+	public function getTablesNames() {
+		return self::TABLES;
+	}
+
+	/**
+	 * @covers ::getCredentialsByVaultId
+	 */
+	public function testGetCredentialsByVaultId() {
+		$expected = $this->findInDataset(
+			self::TABLES[0],
+			'vault_id',
+			$this->dataset->getRow(0)['vault_id']
+		);
+
+		$expected = $this->filterDataset($expected, 'vault_id', $expected[0]['vault_id']);
+
+		/**
+		 * @var Credential[] $expected
+		 */
+		foreach ($expected as &$value) $value = Credential::fromRow($value);
+
+		$data = $this->mapper->getCredentialsByVaultId(
+			$expected[0]->getVaultId(),
+			$expected[0]->getUserId()
+		);
+
+		$this->assertCount(count($expected), $data);
+		$this->assertEquals($expected, $data);
+	}
+
+	/**
+	 * @covers ::getRandomCredentialByVaultId
+	 */
+	public function testGetRandomCredentialByVaultId() {
+		$row = $this->dataset->getRow(0);
+
+		$data = $this->mapper->getRandomCredentialByVaultId(
+			$row['vault_id'],
+			$row['user_id']
+		);
+		$this->assertCount(1, $data);
+
+		$tmp = $this->findInDataset(self::TABLES[0], 'vault_id', $row['vault_id']);
+		$tmp = $this->filterDataset($tmp, 'user_id', $row['user_id']);
+		$tmp = $this->filterDataset($tmp, 'id', $data[0]->getId());
+		$this->assertCount(count($tmp), $data);
+
+		$tmp[0] = Credential::fromRow($tmp[0]);
+		$this->assertEquals($tmp, $data);
+	}
+
+	/**
+	 * @covers ::getExpiredCredentials
+	 */
+	public function testGetExpiredCredentials() {
+		$expired = [];
+
+		for ($i = 0; $i < $this->dataset->getRowCount(); $i++) {
+			$row = $this->dataset->getRow($i);
+			if ($row['expire_time'] > 0 && $row['expire_time'] < Utils::getTime()){
+				$expired[] = Credential::fromRow($row);
+			}
+		}
+
+		$data = $this->mapper->getExpiredCredentials(Utils::getTime());
+		$this->assertNotCount(0, $data, "Not any expired credentials in the dataset?");
+		$this->assertCount(count($expired), $data);
+		$this->assertEquals($expired, $data);
+	}
+
+//	/**
+//	 * @covers ::getCredentialById
+//	 */
+//	public function testGetCredentialById() {
+//
+//	}
+}
\ No newline at end of file